Martin Cartwright, the acting secretary of the NSW branch of the NUW, released a statement on Friday saying the state branch of the union had written to the NSW branch of the ALP "to advise of our disaffiliation from the party, effective immediately".

"Our union is undergoing a series of governance changes, and it is important that our entire team is given the opportunity to focus on this important process," the statement said.

"The decision to step back will allow us to focus on the issues affecting our membership at this time.

"We look forward to re-affiliating with the party in due course."

The Royal Commission into Trade Union Governance and Corruption last year heard evidence that union credit cards were used to buy a tattoo for former secretary Derrick Belan, and on dating websites, Lego, sunglasses, holidays, Tiffany jewellery and other goods totalling tens of thousands of dollars.

Unions NSW suspended the union last month in response to the allegations of the inappropriate spending and poor governance.

Unions NSW suspended the troubled Health Services Union NSW after similar allegations of spending by former officials Kathy Jackson, Michael Williamson and Craig Thompson came to light.

The HSU also disaffiliated itself from the ALP to address corruption and poor governance within the union. It is now working towards re-entering the ALP fold.

It is understood the NUW would also seek to restore its affiliation with the ALP after a process of rebuilding its executive and addressing corruption allegations raised by the royal commission.

Brothers and former party officials Derrick and Nick Belan also face possible expulsion from the NSW branch of the ALP. The party's administration committee has voted to refer a call for their expulsion to the internal appeal tribunal. Both men have been suspended from the party.

NSW Labor acting general secretary, Kaila Murnain, on Friday said she had been advised that the NUW had decided to disaffiliate with the NSW Branch of the Australian Labor Party.

"This decision will provide the union the time it needs to focus on a number of important issues for its membership," she said.

"I wish the new leadership team at the National Union of Workers well during this difficult time.

"We fully anticipate the union will re-affiliate to the Party in the near future."

The decision comes on the eve of next month's ALP conference.

Earlier this month, Fairfax Media reported that unions were preparing a public show of strength at next month's party conference in a bid to secure blanket opposition to any increase in the GST.

The move, at NSW Labor leader Luke Foley's first conference as party leader, is being viewed as a backlash to Mr Foley's comments about being open to considering a GST rise in certain circumstances and his determination to be independent of unions on policy matters.

Fairfax Media understands the right wing United Services Union is proposing that the conference adopts opposing any increase in the GST as Labor policy - a move that would bind all MPs to the position.